This is a short chapter on custom functions, so this will therefore be a short post.  As you know, functions are the bread-and-butter of PHP code as they allow you to encapsulate repeatable code in a reusable manner, making the transition away from spaghetti code. 

• Just like variable names, function names must only contain letters, numbers, and underscores while not starting with a number.

Return Values

• Funny thing about functions in PHP, they ALWAYS return something (NULL by default), there is no void (only ZUUL).
• Functions can be forced to return by reference by placing an ampersand (&) before the function name.
  function &retRef() { }

  1. </li>
  2. </ul>
  3. <h3>Functional Scope</h3>
  4. <ul>
  5. <li>All variables created in a function are destroyed upon exiting. </li>
  6. <li>Variables declared outside of a function are not accessible inside unless passed by parameters or through use of the Global scope. </li>
  7. <li><strong>Global scope</strong> (used through the global command or $GLOBALS superglobal array) allows variables to be read and modified inside a function without the need to pass as parameters.</li>
  8. </ul>
  9. <h3>Arguments</h3>
  10. <ul>
  11. <li>PHP will only yell at you if you provide<strong> too few arguments</strong> to a function.&#160; In theory, you can provide as many arguments as you want as long as it is equal to or more than the arguments declared by the function.
  12. <pre lang="php">function simple($one, $two) {}
  13.  
  14. simple($a, $b, $c, $d, $e);
• Arguments can be set as optional by providing a default value.
  function optArguments($required, $optional = false) {}

  1. </li>
  2. <li>If you want a <strong>variable number of arguments,</strong> there are three functions designed to handle that.
  3. <ul>
  4. <li><strong>func_num_args():</strong> returns the number of arguments that were passed. </li>
  5. <li><strong>func_get_arg($num):</strong> returns the value of the $num argument. </li>
  6. <li><strong>func_get_args():</strong> returns an array of all the arguments. </li>
  7. </ul>
  8. <p>Here is an example: </p>
  9. <pre lang="php">function varArgs() {
  10.   if (func_num_args() == 0)
  11.     return "Please provide at least ONE argument";
  12.   $args = func_get_args();
  13.   foreach ($args as $arg)
  14.     echo $arg."\n";
  15. }
• Arguments can also be forced to be passed by reference by preceding them with the ampersand (&).
  function passByRef(&$myArg) {

  1.   $myArg = 42;
  2. }

Well, that was it for this chapter.  Simple and straight to the point.  Tomorrow I start chapter 3, Arrays.  Woohoo!